1. Field of the Invention
The present invention relates to a method of processing color photographic materials (particularly, reversal color photographic materials) and, more particularly, it relates to an improvement in a method for color photographic processing using a novel bleach accelerator.
2. Description of the Prior Art
In general, the fundamental processing steps for silver halide color photographic materials include a color development step and a silver removal step. That is, when an image-wise exposed silver halide color photographic material is processed in a color development step, the silver halide is reduced by a color developing agent to form silver and the oxidized color developing agent reacts with color formers to provide dye images. Thereafter, the color photographic material is processed in a silver removal step, whereby the silver formed in the previous step is oxidized by the action of an oxidizing agent (usually called a "bleaching agent"), dissolved by a complexing agent for silver ion usually called a "fixing agent", and removed from the photographic material. Thus, only dye images remain on the photographic material. When development for color photographic materials is practiced, auxiliary processing steps are, if desired, employed in addition to the above-described color development step and silver removal step for maintaining good photographic and physical qualities of the dye images. For example, a hardening bath for preventing light-sensitive layers from being excessively softened during processing, a stop bath for effectively stopping the development reaction, an image stabilization bath for stabilizing the dye images formed, and a bath for removing the backing layer of a support are used.
Furthermore, the above-described silver-removal step can be performed in one step using a blix bath containing the combination of a bleaching agent and a fixing agent and in two steps using a bleaching bath and a fixing bath.
In general, potassium ferricyanide is used in the bleach bath as an oxidizing agent. However, a bleach bath using potassium ferricyanide has the disadvantages that the bleach bath must be, when fatigued, exchanged for fresh bleach bath and also the ferricyanide ions and ferrocyanide ions, which are the reduced form of ferricyanide ions, present in water, which must be discharged by overflow during processing or by water washing after bleaching form cyan compounds by photochemical oxidation. These cyan compounds are very toxic and, thus, give rise to serious problems. Therefore, the development of a bleaching agent which can be used as a substitute for potassium ferricyanide has been desired.
On the other hand, bleaching agents other than potassium ferricyanide, potassium dichromate, ferric ion complexes, persulfates, quinones, copper salts, etc., have hitherto been used but they have the disadvantages that the oxidizing capability is weak and the treatment thereof is troublesome.
Ferric ion complexes are sometimes used as a bleaching agent in a blix bath for color photographic papers (as disclosed in, for example, German Pat. Nos. 866,605 and 966,410 and British Pat. Nos. 746,567, 933,088 and 1,014,396). However, since a blix bath containing such a ferric ion complex shows a weak oxidative capability, a blix bath is rarely used for processing high-sensitive silver halide photographic materials, in particular, in-camera type color photographic materials using silver iodobromide.
Also, as the case may be, the ferric ion complex may be added to a bleach bath together with a bromide. However, a long time is required for a bleach bath containing a ferric ion complex as a bleaching agent for bleaching to be performed due to the weak oxidative capability of such a bleach bath as in the case of a blix bath.
Recently, from the standpoint of simplifying the processing for color photographic materials and preventing environmental pollution, a bleaching process using mainly a complex salt of ferric ion and an aminopolycarboxylic acid, such as, for example, an iron (III)-ethylenediaminetetraacetic acid complex, has been mostly used. However, a bleach bath or blix bath containing an iron (III) complex of this kind has the disadvantage that a long period of time for bleaching is required due to the weak oxidative capability of the iron (III) complex.
Therefore, to increase the oxidative capability of a bleach bath or blix bath containing a bleaching agent of this kind to decrease the period of time required for bleaching, various bleach accelerators have hitherto been proposed as disclosed in, for example, U.S. Pat. No. 3,893,858, British Pat. No. 1,337,346 and Czechoslovakian Pat. No. 134,864.
However, some of these accelerators have a poor accelerating action in a blix bath and the accelerators which have satisfactory characteristics when they are added to any of a bleach bath, a blix bath or a pre-bath (that is, a bath employed between a color development bath and a bleach bath or blix bath) are rare.